The last and largest of the morels to fruit in the spring, the yellow morel is the king of all of the morel species. Morchella americana starts to appear around 3 weeks after the black morels start.
Yelow morels start to appear as small baby grey mushrooms. People commonly refer to them as the “grey morel” however they are just an immature stage of the Morchella americana.
Don’t be to impatient and pick these young babies as they will grow for weeks as long as they do not dry out or freeze. A small dime size grey can grow into the size of a baseball! (See https://www.mushroomhole.com/morel-growth/ )
A hat full of little greys can turn into a bushel basket of big yellows in a couple weeks time. Don’t expect to see much of a change in growth over night, or even a couple days. They take time to get big. The wait is worth the reward. Cover them up if you’re worried about someone else finding them!
Morchella americana can be found in all kind of places, dying elm trees, ash trees, aspen stands, white pines, old orchards, and even in fields and along road sides with no trees around. I always have my eyes open for them in the spring. They can even be found in the city growing in parks and yards.